Method of estimating battery life, battery life estimation device, electric vehicle, and electric power supply apparatus

ABSTRACT

A method of estimating a battery life includes: for a secondary battery having a degradation rate R when X days have elapsed after initial charge of the secondary battery, calculating a degradation estimation value (X+Y) days after the initial charge from degradation master data, the degradation master data being identified with use of conditions of temperature T provided for the calculation and a battery state S provided for the calculation; and deriving number of elapsed days Xcorr giving the degradation rate R based on the identified degradation master data, and calculating the degradation estimation value (Xcorr+Y) days after the initial charge from the identified degradation master data.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Priority PatentApplication JP 2012-228122 filed Oct. 15, 2012, the entire contents ofwhich are incorporated herein by reference.

BACKGROUND

The present disclosure relates to a method of estimating a life, forexample, of a lithium ion secondary battery or the like, to a lifeestimation device, for example, for a lithium ion secondary battery orthe like, to an electric vehicle, and to an electric power supplyapparatus.

As an electric power source in a power field including, for example, anelectric vehicle, a hybrid vehicle, an electric motorcycle, and anelectric power-assisted bicycle or in an electric storage fieldincluding, for example, load leveling, peak shift, and backup, a lithiumion secondary battery has been widely used.

In using the secondary battery in the power field or the electricstorage field, it is largely necessary to accurately estimate a life ofthe secondary battery. One reason for this is that, in the case where abattery life is wrongly estimated longer than actual life and thebattery life expires while in use of an apparatus, it may lead to asevere damage or a severe accident. Another reason for this is that, incontrast, in the case where the battery life is estimated excessivelyshort, the battery is renewed unnecessarily. Further, since a battery isbuilt into a large-scale system as part thereof, it is not necessarilypossible to renew an old battery anytime. In such a system, it isnecessary to renew the old battery according to a plan while previouslyconsidering a usage state and the like based on an estimated batterylife. From the foregoing points, an accurate method of estimating a lifeof a battery has been strongly desired.

For example, in Japanese Unexamined Patent Application Publication No.2007-322171 (JP2007-322171A), a technology to calculate degradationlevel and a remaining capacity of an automotive battery is disclosed.Further, it has been known that a full-charge capacity is estimated fromvariation in internal resistance of a battery and voltage drop of thebattery.

SUMMARY

If a technology of estimating capacity degradation is available,frequency shortage of measurement evaluations is allowed to becompensated, and a battery life is allowed to be determined withsufficient time. It has been regarded that determination of a remaininglife of a lithium ion secondary battery is difficult. Therefore, singlecondition varying with time, that is, only a cycle life or only apreservation life has been measured and estimated. Such a method is nota practical method. One reason for this is that an actual secondarybattery is used both in a state of cycles and in a state ofpreservation. Therefore, it has been desired to achieve an estimationmethod suitable for practical use that is allowed to deal with a mixedstate of various conditions varying with time. The technology disclosedin JP2007-322171A and existing life estimation methods are used forobtaining degradation at present, and are not sufficient in terms ofestimating degradation degrees in the future.

It is desirable to provide a method of estimating a life, a lifeestimation device, an electric vehicle, and an electric power supplyapparatus that are capable of accurately estimating a life of asecondary battery.

According to an embodiment of the present technology, there is provideda method of estimating a battery life, the method including:

for a secondary battery having a degradation rate R when X days haveelapsed after initial charge of the secondary battery, calculating adegradation estimation value (X+Y) days after the initial charge fromdegradation master data, the degradation master data being identifiedwith use of conditions of temperature T provided for the calculation anda battery state S provided for the calculation; and

deriving number of elapsed days Xcorr giving the degradation rate Rbased on the identified degradation master data, and calculating thedegradation estimation value (Xcorr+Y) days after the initial chargefrom the identified degradation master data.

According to an embodiment of the present technology, there is provideda battery life estimation device including:

a storage section configured to store a plurality of types ofdegradation master data;

a condition setting section configured to set conditions related totemperature T provided for calculation and a battery state S providedfor the calculation; and

a controller configured to obtain a degradation estimation value,wherein

for a secondary battery having a degradation rate R when X days haveelapsed after initial charge of the secondary battery, the battery lifeestimation device is configured to calculate the degradation estimationvalue (X+Y) days after the initial charge from the degradation masterdata,

the controller is configured to select one of the plurality of types ofdegradation master data with use of the conditions set by the conditionsetting section, and

the controller is configured to derive number of elapsed days Xcorrgiving the degradation rate R based on the identified degradation masterdata, and to calculate the degradation estimation value (Xcorr+Y) daysafter the initial charge from the identified degradation master data.

According to an embodiment of the present technology, there is providedan electric vehicle including

a battery life estimation device including

a storage section configured to store a plurality of types ofdegradation master data,

a condition setting section configured to set conditions related totemperature T provided for calculation and a battery state S providedfor the calculation, and

a controller configured to obtain a degradation estimation value,wherein

for a secondary battery having a degradation rate R when X days haveelapsed after initial charge of the secondary battery, the battery lifeestimation device is configured to calculate the degradation estimationvalue (X+Y) days after the initial charge from the degradation masterdata, the secondary battery being configured to generate drive power ofthe vehicle,

the controller is configured to select one of the plurality of types ofdegradation master data with use of the conditions set by the conditionsetting section, and

the controller is configured to derive number of elapsed days Xcorrgiving the degradation rate R based on the identified degradation masterdata, and to calculate the degradation estimation value (Xcorr+Y) daysafter the initial charge from the identified degradation master data.

According to an embodiment of the present technology, there is providedan electric power supply apparatus including

a battery life estimation device including

a storage section configured to store a plurality of types ofdegradation master data,

a condition setting section configured to set conditions related totemperature T provided for calculation and a battery state S providedfor the calculation, and

a controller configured to obtain a degradation estimation value,wherein

for a secondary battery having a degradation rate R when X days haveelapsed after initial charge of the secondary battery, the battery lifeestimation device is configured to calculate the degradation estimationvalue (X+Y) days after the initial charge from the degradation masterdata, the secondary battery being configured to generate alternatingelectric power,

the controller is configured to select one of the plurality of types ofdegradation master data with use of the conditions set by the conditionsetting section, and

the controller is configured to derive number of elapsed days Xcorrgiving the degradation rate R based on the identified degradation masterdata, and to calculate the degradation estimation value (Xcorr+Y) daysafter the initial charge from the identified degradation master data.

By the method of estimating a battery life according to the embodimentof the present disclosure, even in a state in which conditions such ascharge and discharge cycles, preservation, and various environmentaltemperatures are varied, a life is estimated with little error.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, and are intended toprovide further explanation of the technology as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated in and constitutea part of this specification. The drawings illustrate embodiments and,together with the specification, serve to explain the principles of thetechnology.

FIG. 1 is a schematic diagram used for explanation of a method ofestimating a life of a battery.

FIG. 2 is a schematic diagram used for explanation of a method ofestimating a life according to an embodiment of the present disclosure.

FIG. 3 is a schematic diagram used for explanation of the method ofestimating a life according to the embodiment of the present disclosurein the case where a plurality of conditions are varied.

FIG. 4 is a block diagram schematically illustrating a life estimationdevice according to an embodiment of the present disclosure.

FIG. 5 is a block diagram of an example of an actual degradation ratemeasurement section in the life estimation device according to theembodiment of the present disclosure.

FIG. 6 is a schematic diagram used for explanation of Example 1according to the embodiment of the present disclosure.

FIG. 7 is a schematic diagram used for explanation of Example 2according to the embodiment of the present disclosure.

FIG. 8 is a block diagram of a first example of application examples towhich an electric power source device according to an embodiment of thepresent disclosure is applicable.

FIG. 9 is a block diagram of a second example of the applicationexamples to which the electric power source device according to theembodiment of the present disclosure is applicable.

DETAILED DESCRIPTION

Embodiments described below are some preferred specific examples of thepresent disclosure. In the embodiments, various limitations that may betechnically preferable are given. However, in the following description,the scope of the present disclosure is not limited to these embodimentsunless a description to limit thereto is given.

[Example of Lithium Ion Secondary Battery]

In an embodiment of the present disclosure, one example of batteriesused therein may be a lithium ion secondary battery containing a cathodeactive material and graphite as an anode active material. Although acathode material is not particularly limited, the cathode material maypreferably contain a cathode active material having an olivinestructure. More preferable examples of the cathode active materialhaving an olivine structure may include a lithium iron phosphatecompound (LiFePO₄) and a lithium iron complex phosphate compound(LiFe_(x)M_(1-x)O₄: M represents one or more types of metal, and x is inthe range of 0<x<1) containing a different atom. Further, in the casewhere M represents two or more types of metal, selection is made so thatthe total of inferior numbers of the respective types of metal becomes1-x. Examples of M may include transition elements, group IIA elements,group IIIA elements, group IIIB elements, and group IVB elements. Inparticular, one or more of cobalt (Co), nickel, manganese (Mn), iron,aluminum, vanadium (V), and titanium (Ti) may be preferably includedtherein.

In the cathode active material, a coating layer containing a metal oxide(such as a metal oxide configured of an element selected from a groupincluding Ni, Mn, Li, and the like) having a composition different fromthat of the lithium iron phosphate compound or the lithium iron complexphosphate compound, a phosphate compound (such as lithium phosphate),and/or the like may be provided on the surface of the lithium ironphosphate compound or the lithium iron complex phosphate compound.

The graphite in the embodiment of the present disclosure is notparticularly limited. As the graphite, a graphite material used in theindustry may be widely used.

A method of manufacturing an electrode of the battery according to theembodiment of the present disclosure is not particularly limited. As themethod, a method used in the industry may be widely used.

A configuration of the battery in the embodiment of the presentdisclosure is not particularly limited. As the configuration of thebattery, a known configuration may be widely used.

An electrolytic solution used for the embodiment of the presentdisclosure is not particularly limited, and examples thereof may includea liquid electrolytic solution and a gel electrolytic solution. As theelectrolytic solution, an electrolytic solution that is used in theindustry may be widely used.

Preferable examples of a solvent of the electrolytic solution mayinclude 4-fluoro-1,3-dioxolane-2-one (FEC), ethylene carbonate,propylene carbonate, butylene carbonate, vinylene carbonate (VC),dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate,γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, tetrahydrofuran,2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, methylacetate, methyl propionate, ethyl propionate, acetonitrile,glutaronitrile, adiponitrile, methoxyacetonitrile,3-methoxypropionitrile, N,N-dimethylformamide, N-methylpyrrolidinone,N-methyloxazolidinone, nitromethane, nitroethane, sulfolane, dimethylsulfoxide, trimethyl phosphate, triethyl phosphate, ethylene sulfide,and bisrifluoromethyl sulfonyl imide trimethyl hexyl ammonium. Morepreferable examples thereof may include 4-fluoro-1,3-dioxolane-2-one(FEC), ethylene carbonate, propylene carbonate, butylene carbonate,vinylene carbonate (VC), dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, γ-butyrolactone, and γ-valerolactone.

Preferable examples of a support salt of the electrolytic solution mayinclude lithium hexafluorophosphate (LiPF₆),bis(pentafluoroethanesulfonyl)imide lithium (Li(C₂F₅SO₂)₂N), lithiumperchlorate (LiClO₄), lithium hexafluoroarsenate (LiAsF₆), lithiumtetrafluoroborate (LiBF₄), lithium trifluoromethane sulfonate(LiSO₃CF₃), bis(trifluoroethanesulfonyl)imide lithium (Li(CF₃SO₂)₂N),and tris(trifluoroethanesulfonyl)methyl lithium (LiC(SO₂CF₃)₃.

[Outline of Degradation Estimation]

A description will be given of outline of degradation estimationreferring to FIG. 1. FIG. 1 illustrates a relation between time courseand degradation rate. At the time of assembling the battery, batteryelectrodes and the electrolytic solution are enclosed and sealed in anouter package member. Next, the first charge (referred to as the initialcharge) at the rate of 50% or more of a rated capacity of the battery isperformed. A capacity in an unused state is expressed by initialcapacity Capa (0), and a capacity X days after the initial charge isexpressed by Capa (x). Degradation rate R measured t days after theinitial charge is expressed as follows.

R=100−100×Capa(x)/Capa(0) (0≦R≦100)

It is to be noted that a capacity retention rate is determined by100-(capacity degradation rate).

In the embodiment of the present disclosure, after measuring thecapacity on date X, capacity degradation rate is estimated for Y days(0≦X, Y). “X” as the reference date for life estimation is notparticularly limited, and may correspond to a date such as a routineinspection date of the battery that is previously set. That is, “X” maybe selected from within the life range of the battery. For example, inthe case where a routine inspection date of a vehicle is the date X, andthe next routine inspection date of the vehicle is set to a date Y daysafter the date X, whether or not performance of the battery is secureduntil the next routine inspection of the vehicle is allowed to beestimated.

Y is a value representing how many days after the date X as thereference date for life estimation the capacity degradation is to beestimated. Y may be arbitrarily selected according to the purpose ofestimation. Upon estimating the degradation Y days after, as conditions,temperature (=T), SOC (State of Charge) (=S), and the number of days(=Y) are designated to calculate an estimated value. It is to be notedthat, instead of SOC, DOD (Depth of Discharge) may be used. SOC and DODare collectively referred to as “battery state”.

In the embodiment of the present disclosure, as conditions in theestimation time period (Y days), a plurality of conditions (Z1, Z2, . .. , Zn) are allowed to be used. A description will be given below of abuildup method of degradation when the condition transition is performedfrom Zn−1 to Zn. The embodiment of the present disclosure may becharacterized in the buildup method of degradation.

The foregoing cathode active material having an olivine structure hasextremely superior chemical stability. That is, degradation with timedue to the cathode is negligibly small, and cell capacity loss isdetermined by a loss amount of lithium due to a side reaction on thesurface of the anode graphite. Therefore, in the case where a celldegraded to the capacity degradation rate R % is further usedcontinuously under another conditions, a loss amount of lithiumcorresponding to the degradation rate R % may be taken over at the timeof start of the next use thereof. As a result, buildup calculation ofthe degradation rate in the case of switching conditions is allowed tobe performed.

As an example, a degradation estimation value is obtained wheredegradation rate after actual use for X days is R %, and in a case thatconditions are set so that time period is Y, the temperature T is A degC, and SOC(S) is b %. In FIG. 2, a dashed curve 1 is a degradationmaster curve corresponding to new conditions (T=A deg C, S=b %) in thecase of performing degradation estimation. The degradation master curveis previously obtained by a mathematical expression, and is stored in anonvolatile memory as a table. Referring to the table, the degradationestimation value is obtainable. Alternatively, the degradationestimation value is obtainable by a mathematical expression (program).By designating conditions, a corresponding degradation master curve isdetermined

In the degradation master curve 1 under the new conditions forperforming degradation estimation, by performing new degradationestimation with time for Y days from a point (point of date Xcorr)corresponding to the degradation rate R %, the degradation estimationvalue Y days after is obtained. That is, in the embodiment of thepresent disclosure, the actual degradation rate R (%) is shifted inparallel with the horizontal axis (the actual number of elapsed days ofthe battery), and the crossing point between the shifted location andthe degradation master curve 1 is regarded as the number of days Xcorr.As described above, the date when switching is made to the newconditions is not the date X, and is converted to a new day, that is,the date Xcorr.

As a method different from that of the embodiment of the presentdisclosure, a simple buildup method of degradation rate can bementioned. For example, capacity degradation rate in the case where abattery is preserved at 45 deg C. and at the rate of SOC of 100% for onemonth from the initial charge is as assumed to be 5%.

Further, capacity degradation rate in the case where the battery ispreserved at 60 deg C. and at the rate of SOC of 100% for one month fromthe initial charge is as assumed to be 10%.

Capacity degradation rate is obtained in the case where one month haselapsed from the initial charge under the condition of 45 deg C., andcontinuously, one month has elapsed under the condition of 60 deg C. Oneof the methods thereof is a method of multiplying one degradation rateby the other degradation rate. That is, (1−0.05)×(1−0.1)=0.855 isobtained. In this method, degradation is obtained as 14.5%. In such amethod, in the variation with time, initial time period with largedegradation is redundantly counted, and therefore, degradation isevaluated excessively large.

Further, a method of adding degradation rates (5+10=15%, degradation:0.85%) also leads to estimation with severe inaccuracy.

The degradation master curve is a variation curve of battery capacitydegradation rate with respect to time in the case where a battery ispreserved (or cycled) at constant temperature and constant SOC (or DOD).The degradation master curve may be obtained by actual degradation dataof the battery. However, various data is necessary, and time period ofdata collection with time may be long, for example, for about 10 years.Therefore, it is not practical to construct the degradation master curveonly by measured data.

The degradation master data in the embodiment of the present disclosuremay be preferably values obtained by calculation based on a mathematicalexpression. More preferably, the degradation master data in theembodiment of the present disclosure may be a value calculated based onproduct of a value calculated from temperature of an outer wall of abattery, a value calculated from the number of days which have elapsedafter the initial charge of the battery, and a value calculated from abattery state such as SOC.

Further, more preferable example may be as follows. The value calculatedfrom the temperature T of the outer wall of the battery may becalculated using an expression including exp (−A/T) (T is absolutetemperature). The value calculated from the number of days which haveelapsed after the initial charge of the battery may be calculated froman expression including (the number of days which have elapsed) ̂B (“̂”represents power) (where 0.3<B<0.7 holds). The value calculated from thestate of charge SOC of the battery may be calculated using an expressionincluding exp (C×SOC/T). A, B, and C may be preferably obtained byfitting of the data of the battery measured with time. C representsdependence of degradation on time. C is from 0.1 to 1.5 both inclusive,and may be preferably from 0.35 to 0.65 both inclusive.

In the expression of the degradation master curve in the embodiment ofthe present disclosure, the temperature T does not refer to ambienttemperature at which a battery cell is located, but refers totemperature of the outer surface of the battery cell. In the expressionof the degradation master curve in the embodiment of the presentdisclosure, in the case where a battery is preserved, the SOC itself ofthe battery during preservation may be used. In contrast, in the casewhere SOC is varied with time when, for example, a battery is in cycle,a time average value in the range of SOC is allowed to be used. It is tobe noted that the number of cycles in the number of days which haveelapsed has no relation with estimation of a life, as long as the timeaverage value of SOC is the same.

In the case where degradation is not linearly varied with respect toSOC, a weighted average may be more preferably obtained for each SOCpoint. For example, considering that a measured degradation value orcapacity degradation is caused by a reduction side reaction on the anodegraphite, each degradation speed ratio for each SOC may be obtained bythe following expression, and each SOC variation point is allowed to beweighted by each of the degradation speed ratios.

Each degradation speed ratio for each SOC may be obtained with the useof specific degradation speed=exp (αFη/RT) where η represents (1-(anodegraphite electric potential to Li)), α=0.5, R=8.314, F=96485, and Trepresents battery temperature (K°). Each SOC variation point may beweighted by such each degradation speed ratio.

[Example of Degradation Estimation]

A description will be given of an example of degradation estimationreferring to FIG. 3. FIG. 3 illustrates degradation master curves 1 a, 1b, 1 c, and 1 d and degradation master curves 2 a, 2 b, 2 c, and 2 d.The degradation master curves 1 a to 1 d are degradation master curvesin the case where the temperature T is A, and correspond to cases whereSOC are a %, b %, c %, and d %, respectively. The degradation mastercurves 2 a to 2 d are degradation master curves in the case where thetemperature T is B, and correspond to cases where SOC are a %, b %, c %,and d %, respectively.

In FIG. 3, thick lines indicate transition of variation in degradationrate as descried below.

The initial charge is performed at the time of t=0. As indicated bycurve 3, a battery is actually used until the time of t=X0 when anactual capacity of the battery is measured. The actual degradation rateR % is obtained.

Next, setting is made so that Y1 days are to elapse under conditionsthat temperature is A, and SOC is b %. The setting is made by a user.Correspondingly to such conditions, the degradation master curve 1 b isselected. As described above, in the case where the battery degraded tothe capacity degradation rate R % is further used continuously underanother condition, a loss amount of lithium corresponding to thedegradation rate R % may be taken over at the time of start of the nextuse thereof. Therefore, the actual degradation rate R (%) is shifted inparallel with the horizontal axis (the actual number of elapsed days ofthe battery), and the crossing point between the shifted location andthe degradation master curve 1 b is the date X1corr, which is regardedas the switching date to the new conditions. During the time period fromX1corr to a date Y1 days after X1corr, degradation rate is predicted tobe varied as indicated by thick line 4 on the degradation master curve 1b. The number of charges and discharges during the time period of the Y1days may be arbitrary. The same may be applied to other preservationtime period.

Next, setting is made so that Y2 days are to elapse under conditionsthat temperature is B, and SOC is b %. Correspondingly to suchconditions, the degradation master curve 2 b is selected. A degradationestimation value at the end of the thick line 4 is shifted in parallelwith the horizontal axis (the actual number of elapsed days of thebattery), and the crossing point between the shifted location and thedegradation master curve 2 b is date X2corr, which is regarded as theswitching date to the new conditions. During the time period from X2corrto the date Y2 days after X2corr, degradation rate is predicted to bevaried as indicated by thick line 5 on the degradation master curve 2 b.

Next, setting is made so that Y3 days are to elapse under conditionsthat temperature is B, and SOC is c %. Correspondingly to suchconditions, the degradation master curve 2 c is selected. A degradationestimation value at the end of the thick line 5 is shifted in parallelwith the horizontal axis (the actual number of elapsed days of thebattery), and the crossing point between the shifted location and thedegradation master curve 2 c is date X3corr, which is regarded as theswitching date to the new conditions. During the time period from X3corrto the date Y3 days after X3corr, degradation rate is predicted to bevaried as indicated by thick line 6 on the degradation master curve 2 c.

Next, setting is made so that Y4 days are to elapse under conditionsthat temperature is B, and SOC is a %). Correspondingly to suchconditions, the degradation master curve 2 a is selected. A degradationestimation value at the end of the thick line 6 is shifted in parallelwith the horizontal axis (the actual number of elapsed days of thebattery), and the crossing point between the shifted location and thedegradation master curve 2 a is date X4corr, which is regarded as theswitching date to the new conditions. During the time period from X4corrto the date Y4 days after X4corr, degradation rate is predicted to bevaried as indicated by thick line 7 on the degradation master curve 2 a.

As a result of the foregoing process, a degradation estimation value ofthe battery at the time when (Y1+Y2+Y3+Y4) days have elapsed after thetime point of X0 is obtained. For example, in the case of a batterymounted on an electric vehicle, degradation rate of the battery at thetime of the next vehicle inspection is allowed to be estimated where X0is time point of the present vehicle inspection, and the time pointafter the (Y1+Y2+Y3+Y4) days have elapsed is a scheduled date of thenext vehicle inspection. The foregoing transition of the conditions ismerely an example, and various transitions are possible. However, inconsideration of actual conditions such as types of electric storagedevices (an electric vehicle, a hybrid vehicle, an electric powerstorage device in a house, and the like), usage purposes of batteries(professional use, household use, and the like), and usage areas (a coldarea, a warm area, and the like), transition of conditions according toa practical case is allowed to be set to some degrees. For example, amanufacturer such as an automotive company may provide information onthe foregoing transition of conditions.

[Example of Degradation Estimation Device]

FIG. 4 illustrates outline of a degradation estimation device to whichthe embodiment of the present disclosure is applied. In FIG. 4,information on transition of conditions is inputted from a conditioninput section 12 to a microcontroller unit (noted as MCU in FIG. 4) 11.As described above, the conditions (temperature, SOC, and elapsed days)are inputted. In general, a plurality of conditions are inputted inorder.

Degradation master curve data is inputted from a master curve memory(nonvolatile memory) 13 to the microcontroller unit 11. As describedabove, the degradation master curve data is data obtained by performingfitting of data of a battery measured with time on data obtained by amathematical expression, obtaining each degradation speed ratio for eachSOC, and performing weighting on each SOC variation point by each of thedegradation speed ratios. The degradation master curve data ispreviously stored.

Further, measured actual degradation rate data is supplied from anactual degradation rate measurement section 15 to the microcontrollerunit 11. The actual degradation rate measurement section 15 measuresdegradation rate at present of a battery section 16. An output section14 is connected to the microcontroller unit 11. A degradation estimationvalue in set conditions may be displayed and the degradation estimationvalue may be printed by the output section 14.

Schematically, the degradation rate measurement section 15 is configuredas illustrated in FIG. 5. A current measurement section 22 and a chargeand discharge control section 23 are inserted in a current path of thebattery section 16. A current (a charge current or a discharge current)measured by the current measurement section 22 is supplied to amicrocontroller unit 21. The microcontroller unit 21 generates a controlsignal to control the charge and discharge control section 23.

Data of initial capacity Capa (0) is stored in a nonvolatile memory inthe microcontroller unit 21. For example, a discharge current in thecase where the battery section 16 is charged until a full-charged stateand full discharge is performed from the full-charged state isintegrated by the microcontroller unit 21. Thereby, a capacity Capa (x)X days after the initial charge is obtained. Further, the actualdegradation rate R % is obtained by the following expression.

R=100−100×Capa(x)/Capa(0) where 0≦R≦100 holds.

(capacity retention rate)=100−(capacity degradation rate) holds.

In the foregoing method of measuring an actual degradation rate, acapacity from a full-charged state (SOC=100%) to a full-discharge state(SOC=0%) is measured. By comparing such a capacity at the time of use ofa battery to a battery capacity before starting use of the battery, adegradation state is obtainable.

However, performing the foregoing measurement at the same time as actualuse of a battery to obtain a full-discharged state of the battery maycorresponds to, for example, a state that a vehicle loses runningcapacity in the case where the battery is used for the vehicle, or astate that backup ability is lost in the case where the battery is usedfor a backup electric power source. Such states are not allowable.Therefore, in the case where an apparatus is in use, a degradation ratemay be estimated by a method already known as a method of measuring anactual degradation rate. For example, a degradation rate of a batterymay be estimated from variation in internal resistance of the battery,voltage drop of the battery, and/or the like.

EXAMPLES

A description will be given in detail of specific examples of theembodiment of the present disclosure. However, examples thereof are notlimited thereto.

Example 1

A coin-type secondary battery having a capacity of 5 mAh was fabricatedwith the use of graphite as an anode active material and LiFePO₄ as acathode active material. After sealing thereof, charge was performed bya constant current and constant voltage method for 7.5 hours at 3.6 V,at 1 mA, and at room temperature, and subsequently, discharge wasperformed at 1 mA until the voltage reached 2.0 V at room temperature.Again, charge was performed for 2.5 hours at a constant voltage of 3.6 Vand at a constant current of 2.5 mA, and subsequently, discharge wasperformed at a current of 2.5 mA until the voltage reached 2.0 V. Anobtained discharge capacity of 5.0 mAh was regarded as the initialcapacity. Next, as illustrated in Table 1, charge and discharge andpreservation with time were performed.

TABLE 1 Degradation estimation conditions Stage 1 2 3 4 5 6 7 TypePreservation Capacity Preservation Preservation PreservationPreservation Estimated measurement capacity Temperature 35 deg C. 35 degC. 45 deg C. 60 deg C. 35 deg C. — SOC 100 100 100 100 100 — Time period90 60 30 30 30 — (days) Measured capacity 91.1% Measured 83.2% retentionrate retention rate Estimation of the 82.6% embodiment of the presentinvention Comparative example 59.5% (addition) Comparative example 65.5%(multiplication)

A description will be given of an example of degradation rate variationreferring to Table 1 and FIG. 6. FIG. 6 illustrates degradation mastercurves 31, 32, and 33. The degradation master curve 31 corresponds tothe conditions that temperature T is 35 deg C. and SOC is 100%. Thedegradation master curve 32 corresponds to the conditions thattemperature T is 45 deg C. and SOC is 100%. The degradation master curve33 corresponds to the conditions that temperature T is 60 deg C. and SOCis 100%.

[Stage 1]

After charge was performed for 2.5 hours at a constant voltage of 3.6 Vand at a constant current of 2.5 mA at room temperature, the battery waspreserved for 90 days at 35 deg C. in a constant temperature bath (athick line 33 of the degradation master curve 31). After temperature wasdecreased down to room temperature, discharge was performed at a currentof 2.5 mA until the voltage reached 2.0 V.

[Stage 2]

Subsequently, charge was performed for 2.5 hours at a constant voltageof 3.6 V and at a constant current of 2.5 mA. Subsequently, dischargewas performed at a current of 2.5 mA until the voltage reached 2.0 V. Anobtained discharge capacity value was divided by the initial capacityvalue (5.0 mAh) to obtain capacity retention rate of 91.1%.

[Stage 3]

After charge was performed for 2.5 hours at a constant voltage of 3.6 Vand at a constant current of 2.5 mA at room temperature, the battery waspreserved for 60 days at 35 deg C. in a constant temperature bath (athick line 34 of the degradation master curve 31). After temperature wasdecreased down to room temperature, discharge was performed at a currentof 2.5 mA until the voltage reached 2.0 V.

[Stage 4]

After charge was performed for 2.5 hours at a constant voltage of 3.6 Vand at a constant current of 2.5 mA at room temperature, the battery waspreserved for 30 days at 45 deg C. in a constant temperature bath (athick line 35 of the degradation master curve 31). After temperature wasdecreased down to room temperature, discharge was performed at a currentof 2.5 mA until the voltage reached 2.0 V.

[Stage 5]

After charge was performed for 2.5 hours at a constant voltage of 3.6 Vand at a constant current of 2.5 mA at room temperature, the battery waspreserved for 30 days at 60 deg C. in a constant temperature bath (athick line 36 of the degradation master curve 31). After temperature wasdecreased down to room temperature, discharge was performed at a currentof 2.5 mA until the voltage reached 2.0 V.

[Stage 6]

After charge was performed for 2.5 hours at a constant voltage of 3.6 Vand at a constant current of 2.5 mA at room temperature, the battery waspreserved for 30 days at 35 deg C. in a constant temperature bath (athick line 37 of the degradation master curve 31). After temperature wasdecreased down to room temperature, discharge was performed at a currentof 2.5 mA until the voltage reached 2.0 V.

[Stage 7]

Subsequently, charge was performed for 2.5 hours at a constant voltageof 3.6 V and at a constant current of 2.5 mA. Subsequently, dischargewas performed at a current of 2.5 mA until the voltage reached 2.0 V. Anobtained discharge capacity value was divided by the initial capacityvalue (5.0 mAh) to obtain capacity retention rate of 83.2%.

A description will be given below of a process to obtain a degradationestimation value according to Example 1 of the embodiment of the presentdisclosure.

The degradation master curves 31, 32, and 33 of the capacity retentionrate were calculated by the following expressions (T=absolutetemperature).

Degradation rate(%)=23000×[exp(−3368/T)]×[(days)̂0.45]×[exp(3.247×SOC/T)]

Retention rate (%)=100−degradation rate (%)

In the estimation calculation, first, the following values weresubstituted in the foregoing expression, and thereby, degradation rateof 8.9% was obtained (thick line 33).

T=273+35

-   -   days=30    -   SOC=100

Next, the following values were substituted in the foregoing expression,and thereby, degradation rate of 11.2% was obtained (thick line 34).

T=273+35

-   -   days=90+60    -   SOC=100

Next, the date when the degradation rate of 11.2% was obtained at 45 degC. was calculated inversely to obtain days=75.2. The following valueswere substituted in the foregoing expression, and thereby, degradationrate of 13.2% was obtained (thick line 35).

T=273+45

-   -   days=75.1+30    -   SOC=100

Thereafter, the calculation was repeated similarly to obtain theestimation retention rate of 82.6% according to the embodiment of thepresent disclosure. Such a degradation estimation value is a value closeto the measured retention rate of 83.2%.

Comparative Example 1

For a battery fabricated as in Example 1, the initial capacity thereofwas measured. Thereafter, charge was performed for 2.5 hours at aconstant voltage of 3.6 V and at a constant current of 2.5 mA at roomtemperature, the battery was subsequently preserved in a constanttemperature bath. Thereafter, temperature was decreased down to roomtemperature, and discharge was performed at a current of 2.5 mA untilthe voltage reached 2.0 V.

Subsequently, charge was performed for 2.5 hours at a constant voltageof 3.6 V and at a constant current of 2.5 mA. Subsequently, dischargewas performed at a current of 2.5 mA until the voltage reached 2.0 V. Anobtained discharge capacity value was divided by the initial capacityvalue (5.0 mAh) to obtain capacity retention rate based on singlecondition.

The temperature and the number of days related to the foregoingpreservation were: 35 deg C. and 90 days, 35 deg C. and 60 days, 35 degC. and 30 days, 45 deg C. and 30 days, and 60 deg C. and 30 days.

Capacity retention rate under single condition was obtained as follows:35 deg C.

90 days: 91.1%

60 days: 92.6%

30 days: 94.6%

45 deg C.

30 days: 92.6%

60 deg C.

30 days: 88.6%

Retention rate in the case where preservation under a plurality ofconditions (35 deg C. and 90 days, 35 deg C. and 60 days, 45 deg C. and30 days, 60 deg C. and 30 days, and 35 deg C. and 30 days) wascontinuously made was obtained by multiplication. As a result, complexretention rate became 65.5% as shown in the following expression:

0.911×0.926×0.926×0.886×0.946=0.655

On the other hand, in the case where complex degradation rate wasobtained by addition, the result became 40.5% as shown in the followingexpression. Further, retention rate became 59.5% as shown in thefollowing expression.

(1−0.911)+(1−0.926)+(1−0.926)+(1−0.886)+(1−0.946)=0.405

1−0.405=0.595

According to the embodiment of the present disclosure, with respect tothe measured retention rate of 83.2%, the estimation value of 82.6% wasobtained, which showed significantly favorable correspondence. In thecomparative example, the value obtained by multiplication of eachretention ratio of respective unit conditions (35 deg C. and 30 days, 35deg C. and 60 days, 35 deg C. and 90 days, 45 deg C. and 30 days, and 60deg C. and 30 days) was 65.5%, and the retention rate obtained byaddition of each degradation rate was 59.5%. These results were valueslargely different from the measured values. One reason for this is that,simple multiplication or simple addition of retention rates obtainedunder respective conditions results in multiple addition of a value inthe initial time period with large degradation, leading to excessivelylarge evaluation of degradation. In contrast, in the embodiment of thepresent disclosure, the multiple addition of initial degradation isavoided, and therefore, favorable estimation is obtained.

Example 2

A coin-type secondary battery was fabricated as in Example 1, and theinitial capacity thereof was obtained as in Example 1.

Next, as illustrated in Table 2 and FIG. 7, charge and discharge andcycles with time were performed. FIG. 7 illustrates degradation mastercurves 41, 42, and 43. The degradation master curve 41 corresponds toconditions that temperature T is 35 deg C. and SOC is 50%. Thedegradation master curve 42 corresponds to conditions that temperature Tis 45 deg C. and SOC is 50%. The degradation master curve 43 correspondsto conditions that temperature T is 60 deg C. and SOC is 50%. Sincecharge and discharge cycles were performed, SOC was 50% that was half of100%.

TABLE 2 Degradation estimation conditions Stage 1 2 3 4 5 6 7 Type CycleCapacity Cycle Cycle Cycle Cycle Estimated measurement capacityTemperature 45 deg C. 60 deg C. 45 deg C. 35 deg C. 60 deg C. — SOC0-100 0-100 0-100 0-100 0-100 — Time period 60 30 60 90 30 — (days)Measured capacity 93.9% Measured 87.0% retention rate retention rateEstimation of the 86.9% embodiment of the present invention Comparativeexample 68.5% (addition) Comparative example 72.2% (multiplication)

[Stage 1]

A cycle in which discharge was performed at a current of 2.5 mA untilthe voltage reached 2.0 V after charge was performed for 2.5 hours at aconstant voltage of 3.6V and at a constant current of 2.5 mA wasrepeated for 60 days at 45 deg C. in a constant temperature bath (athick line 44 of the degradation master curve 42). After temperature wasdecreased down to room temperature, discharge was performed at a currentof 2.5 mA until the voltage reached 2.0 V.

[Stage 2]

Subsequently, charge was performed for 2.5 hours at a constant voltageof 3.6 V and at a constant current of 2.5 mA. Subsequently, dischargewas performed at a current of 2.5 mA until the voltage reached 2.0 V. Anobtained discharge capacity value was divided by the initial capacityvalue (5.0 mAh) to obtain capacity retention rate of 93.9%.

[Stage 3]

A cycle in which discharge was performed at a current of 2.5 mA untilthe voltage reached 2.0 V after charge was performed for 2.5 hours at aconstant voltage of 3.6 V and at a constant current of 2.5 mA) wasrepeated for 30 days at 60 deg C. in a constant temperature bath (athick line 45 of the degradation master curve 43).

[Stage 4]

A cycle in which discharge was performed at a current of 2.5 mA untilthe voltage reached 2.0 V after charge was performed for 2.5 hours at aconstant voltage of 3.6 V and at a constant current of 2.5 mA wasrepeated for 60 days at 45 deg C. in a constant temperature bath (athick line 46 of the degradation master curve 42).

[Stage 5]

A cycle in which discharge was performed at a current of 2.5 mA untilthe voltage reached 2.0 V after charge was performed for 2.5 hours at aconstant voltage of 3.6 V and at a constant current of 2.5 mA wasrepeated for 90 days at 35 deg C. in a constant temperature bath (athick line 47 of the degradation master curve 41).

[Stage 6]

A cycle in which discharge was performed at a current of 2.5 mA untilthe voltage reached 2.0 V after charge was performed for 2.5 hours at aconstant voltage of 3.6V and at a constant current of 2.5 mA wasrepeated for 30 days at 60 deg C. in a constant temperature bath (athick line 48 of the degradation master curve 43).

[Stage 7]

After temperature was decreased down to room temperature, discharge wasperformed at a current of 2.5 mA until the voltage reached 2.0 V.

Subsequently, charge was performed for 2.5 hours at a constant voltageof 3.6 V and at a constant current of 2.5 mA. Subsequently, dischargewas performed at a current of 2.5 mA until the voltage reached 2.0 V. Anobtained discharge capacity value was divided by the initial capacityvalue (5.0 mAh) to obtain measured retention rate of 87.0%.

A description will be given below of a process to obtain a degradationestimation value according to Example 2 of the embodiment of the presentdisclosure.

The degradation master curves 41, 42, and 43 of capacity retention ratewere calculated by the following expression (T=absolute temperature).

Degradation rate(%)=23000×[exp(−3368/T)]×[(days)̂0.45]×[exp(3.247×SOC/T)]

Retention rate (%)=100−degradation rate (%)

As SOC, an average value of the lowest SOC and the highest SOC of thecycles was used.

In the estimation calculation, first, the following values weresubstituted in the foregoing expression, and thereby, degradation rateof 6.1% was obtained (the thick line 44).

T=273+45

days=60

SOC=50

Next, the date when the degradation rate of 6.1% was obtained at 60 degC. was calculated inversely to obtain days=22. The following values weresubstituted in the foregoing expression, and thereby, degradation rateof 9.0% was obtained (thick line 45).

T=273+60

days=22+30

SOC=50

Thereafter, the calculation was repeated similarly to obtain theestimation retention rate of 86.9% according to the embodiment of thepresent disclosure. Such a degradation estimation value is a value closeto the measured retention rate of 87%.

Comparative Example 2

For a battery fabricated as in Example 2, the initial capacity thereofwas measured. Thereafter, charge was performed for 2.5 hours at aconstant voltage of 3.6 V and at a constant current of 2.5 mA at roomtemperature, and the battery was subsequently preserved in a constanttemperature bath. Thereafter, temperature was decreased down to roomtemperature, and discharge was performed at a current of 2.5 mA untilthe voltage reached 2.0 V.

Subsequently, charge was performed for 2.5 hours at a constant voltageof 3.6 V and at a constant current of 2.5 mA. Subsequently, dischargewas performed at a current of 2.5 mA until the voltage reached 2.0 V. Anobtained discharge capacity value was divided by the initial capacityvalue (5.0 mAh) to obtain capacity retention rate under singlecondition.

The temperature and the number of days related to the foregoing cycleswere: 45 deg C. and 60 days, 60 deg C. and 30 days, and 35 deg C. and 90days.

Capacity retention rate under each single condition was obtained asfollows:

45 deg C. and 60 days: 93.9%

60 deg C. and 30 days: 93.0%

35 deg C. and 90 days: 94.7%

Retention rate in the case where cycles under a plurality of conditions(45 deg C. and 60 days, 60 deg C. and 30 days, 45 deg C. and 60 days, 35deg C. and 90 days, and 60 deg C. and 30 days) were continuously madewas obtained by multiplication. As a result, complex retention ratebecame 72.2% as shown in the following expression:

0.939×0.930×0.939×0.947×0.930=0.722

On the other hand, in the case where complex degradation rate wasobtained by addition, the result became 31.5% as shown in the followingexpression. Further, retention rate became 68.5% as shown in thefollowing expression.

(1−0.939)+(1−0.930)+(1−0.939)+(1−0.947)+(1−0.930)=0.315

1−0.315=0.685

According to the embodiment of the present disclosure, with respect tothe measured retention rate of 87.0%, the estimation value of 86.9% wasobtained, which showed significantly favorable correspondence. In thecomparative example, the value obtained by multiplication of therespective retention rates of the respective unit conditions was 72.2%,and the retention rate obtained by addition of respective degradationrates was 68.5%. These results were values largely different from themeasured values. One reason for this is that simple multiplication orsimple addition of results under respective conditions results inmultiple addition of a value in time period with large initialdegradation, leading to excessively large evaluation of degradation. Incontrast, in the embodiment of the present disclosure, the multipleaddition of initial degradation is avoided, and therefore, favorableestimation is obtained.

Electric Power Storage System in Residence as Application Example

A description will be given of an example in which the embodiment of thepresent disclosure is applied to an electric power storage system for aresidence referring to FIG. 8. For example, in an electric power storagesystem 100 for a residence 101, electric power is supplied from aconcentrated electric power system 102 such as a thermal electric powergenerating system 102 a, a nuclear electric power generating system 102b, and a hydroelectric power generating system 102 c to an electricpower storage apparatus 103 through an electric power network 109, aninformation network 112, a smart meter 107, a power hub 108, and/or thelike. In addition thereto, electric power is supplied from anindependent electric power source such as a domestic power generatingapparatus 104 to the electric power storage apparatus 103. The electricpower supplied to the electric power storage apparatus 103 is stored.With the use of the electric power storage apparatus 103, electric powerused in the residence 101 is supplied to the residence. A similarelectric power storage system may be used not only in the residence 101but also in other buildings.

The residence 101 is provided with the electric power generatingapparatus 104, an electric power consumption apparatus 105, the electricpower storage apparatus 103, a control apparatus 110 to controlrespective apparatuses, the smart meter 107, and a sensor 111 to acquirevarious information. The respective apparatuses are connected throughthe electric power network 109 and the information network 112. As thepower generating apparatus 104, a solar battery, a fuel battery, and/orthe like is used. Generated electric power is supplied to the electricpower consumption apparatus 105 and/or the electric power storageapparatus 103. Examples of the electric power consumption apparatus 105may include a refrigerator 105 a, an air-conditioner 105 b, a television105 c, and a bath 105 d. Further, examples of the electric powerconsumption apparatus 105 may include an electric vehicle 106. Examplesof the electric vehicle 106 may include an electric automobile 106 a, ahybrid automobile 106 b, and an electric motorcycle 106 c.

The electric power storage apparatus 103 is configured of a secondarybattery or a capacitor. For example, the electric power storageapparatus 103 may be configured of a lithium ion battery. The lithiumion battery may be a stationary battery, or a battery used in theelectric vehicle 106. The foregoing embodiment of the present disclosureis applied to estimation of capacity degradation of the electric powerstorage apparatus 103. The smart meter 107 has a function to measure aused amount of commercial electric power and to send the measured usedamount to an electric power company. The electric power network 109 maybe one of direct-current power feeding, alternate current power feeding,and noncontact power feeding, or a combination thereof.

Examples of the various sensors 111 may include a motion sensor, anilluminance sensor, an object sensor, an electric power consumptionsensor, a vibration sensor, a contact sensor, a temperature sensor, andan infrared sensor. Information acquired from the various sensors 111 issent to the control apparatus 110. Due to the information from thesensors 111, a weather state, a human state, and/or the like isperceived, the electric power consumption apparatus 105 is automaticallycontrolled, and energy consumption is allowed to be minimized. Further,the control apparatus 110 is allowed to send information on theresidence 101 to an external electric power company and/or the likethrough the Internet.

The power hub 108 performs a process such as branching of an electricpower line and AC/DC conversion. Examples of a communication method ofthe information network 112 connected to the control apparatus 110 mayinclude a method of using a communication interface such as a UART(Universal Asynchronous Receiver-Transceiver) and a method of utilizinga sensor network based on a wireless communication standard such asBluetooth (registered trade mark), ZigBee, and Wi-Fi. The Bluetooth(registered trade mark) method is applied to multimedia communication,and allows one-to-many communication. ZigBee uses IEEE (Institute ofElectrical and Electronics Engineers) 802.15.4 physical layer. IEEE802.15.4 is a name of a short-range wireless network standard called PAN(Personal Area Network) or W (Wireless) PAN.

The control apparatus 110 is connected to an external server 113. Theserver 113 may be managed by any of the residence 101, an electric powercompany, and a service provider. Examples of information that is sentfrom and is received by the server 113 may include consumer electricpower information, life pattern information, an electric power fee,weather information, natural disaster information, and information onelectric power transaction. Such information may be sent from orreceived by a domestic electric power consumption device (such as atelevision), or may be sent from or received by an out-of-home device(such as a mobile phone). Such information may be displayed on a devicehaving a display function such as a television, a mobile phone, and aPDA (Personal Digital Assistants).

The control apparatus 110 that controls respective parts is configuredof a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM(Read Only Memory), and/or the like. In this example, the controlapparatus 110 is stored in the electric power storage apparatus 103. Thecontrol apparatus 110 is connected to the electric power storageapparatus 103, the domestic power generating apparatus 104, the electricpower consumption apparatus 105, the various sensors 111, and the server113 through the information network 112. For example, the controlapparatus 110 may have a function to adjust a used amount of commercialelectric power and an electric-power-generating amount. It is to benoted that, in addition thereto, the control apparatus 110 may have afunction to perform electric power transaction in the electric powermarket.

As described above, not only electric power generated by theconcentrated electric power system 102 such as the thermal electricpower generating system 102 a, the nuclear electric power generatingsystem 102 b, and the hydroelectric power generating system 102 c, butelectric power generated by the domestic power generating apparatus 104(solar power generation or wind power generation) is also allowed to bestored in the electric power storage apparatus 103. Therefore, even ifelectric power generated by the domestic power generating apparatus 104is varied, control is allowed to be executed so that an electric poweramount sent outside becomes constant, or electric discharge is performedas necessary. For example, electric power obtained by solar powergeneration may be stored in the electric power storage apparatus 103,while electric power in the middle of the night when an electric powerrate is inexpensive may be stored in the electric power storageapparatus 103 and the electric power stored by the electric powerstorage apparatus 103 may be discharged and utilized during daytimehours when an electric power rate is expensive.

In this example, a description has been given of the example in whichthe control apparatus 110 is stored in the electric power storageapparatus 103. However, the control apparatus 110 may be stored in thesmart meter 107, and may be configured by itself. Further, the electricpower storage system 100 may be used for a plurality of households in ahousing complex, or may be used for a plurality of single-family houses.

Electric Power Storage System in Vehicle as Application Example

A description will be given of an example in which the embodiment of thepresent disclosure is applied to an electric power storage system for avehicle referring to FIG. 9. FIG. 9 schematically illustrates an exampleof a configuration of a hybrid vehicle adopting a series hybrid systemto which the embodiment of the present disclosure is applied. The serieshybrid system is an automobile running with the use of anelectric-power/drive-power conversion device with the use of electricpower generated by a power generator moved by an engine or such electricpower that is once stored in a battery.

In a hybrid vehicle 200, an engine 201, a power generator 202, anelectric-power/drive-power conversion device 203, a drive wheel 204 a, adrive wheel 204 b, a wheel 205 a, a wheel 205 b, a battery 208, avehicle control device 209, various sensors 210, and a charge inlet 211are included. The foregoing embodiment of the present disclosure isapplied to estimation of capacity degradation of the battery 208.

The hybrid vehicle 200 runs with the use of theelectric-power/drive-power conversion device 203 as a power source.Examples of the electric-power/drive-power conversion device 203 mayinclude a motor. The electric-power/drive-power conversion device 203 isoperated by electric power of the battery 208, and torque of theelectric-power/drive-power conversion device 203 is transferred to thedrive wheels 204 a and 204 b. It is to be noted that, by usingdirect-current/alternating-current (DC-AC) conversion or reverseconversion (AC-DC conversion) at a necessary point, theelectric-power/drive-power conversion device 203 may be used as analternating current motor or a direct current motor. The various sensors210 control engine frequency through the vehicle control device 209,controls opening level (throttle opening level) of an unillustratedthrottle valve. The various sensors 210 may include a speed sensor, anacceleration sensor, an engine frequency sensor, and/or the like.

Torque of the engine 201 is transferred to the power generator 202.Electric power generated by the power generator 202 due to the torque isallowed to be stored in the battery 208.

When speed of the hybrid vehicle is reduced by an unillustrated brakemechanism, resistance at the time of speed reduction is added to theelectric-power/drive-power conversion device 203 as torque, andregenerative electric power generated by the electric-power/drive-powerconversion device 203 due to the torque is stored in the battery 208.

The battery 208 may be connected to an external electric power source ofthe hybrid vehicle, and thereby, may be supplied with electric powerfrom the external electric power source through the charge inlet 211 asan input port, and may store the received electric power.

Although not illustrated, an information processing device to performinformation processing of vehicle control based on information on asecondary battery may be included. Example of such an informationprocessing device may include an information processing device toperform display of a remaining battery capacity based on information onthe remaining battery capacity.

The description has been given of the series hybrid automobile runningwith the use of the motor using electric power generated by the electricpower generator operated by the engine or such electric power that isonce stored in the battery as an example. However, the embodiment of thepresent disclosure is effectively applicable to a parallel hybridautomobile used by switching three methods of running only by an engine,running only by a motor, and running by the engine and the motor asappropriate with the use of both outputs of the engine and the motor asdrive sources. Further, the embodiment of the present disclosure iseffectively applicable to a so-called electric vehicle running by driveonly by a drive motor without using an engine.

It is possible to achieve at least the following configurations from theabove-described example embodiments and the modifications of thedisclosure.

(1) A method of estimating a battery life, the method including:

for a secondary battery having a degradation rate R when X days haveelapsed after initial charge of the secondary battery, calculating adegradation estimation value (X+Y) days after the initial charge fromdegradation master data, the degradation master data being identifiedwith use of conditions of temperature T provided for the calculation anda battery state S provided for the calculation; and

deriving number of elapsed days Xcorr giving the degradation rate Rbased on the identified degradation master data, and calculating thedegradation estimation value (Xcorr+Y) days after the initial chargefrom the identified degradation master data.

(2) The method according to (1), wherein the secondary battery includesa cathode active material having an olivine structure.(3) The method according to (1) or (2), wherein the secondary battery isa lithium ion secondary battery including LiFePO₄ as a cathode activematerial and including graphite as an anode active material.(4) The method according to (2), wherein the cathode active materialhaving the olivine structure is one of LiFePO₄ and LiMn_(x)Fe_(1-x)PO₄where 0<x<1.(5) The method according to any one of (1) to (4), wherein theconditions in estimation during the Y days are configured of n-number ofconditions Z1, Z2, . . . , Zn where 1≦n, and

transition from first degradation master data to second degradationmaster data is performed to allow final degradation rate in the firstdegradation master data to be start degradation rate in the seconddegradation master data, the first degradation master data beingidentified by the condition Zn−1, and the second degradation data beingidentified by the condition Zn.

(6) The method according to any one of (1) to (5), wherein, as thedegradation master data, a value calculated based on a product of avalue calculated from temperature of an outer wall of the secondarybattery, a value calculated from number of days that have elapsed afterthe initial charge of the secondary battery, and a value calculated froma battery state of the secondary battery is used.(7) The method according to (6), wherein

the value calculated from the temperature T of the outer wall of thesecondary battery is calculated using an expression including exp (−A/T)where T is absolute temperature,

the value calculated from the number of days that have elapsed after theinitial charge of the secondary battery is calculated using anexpression including (the number of days that have elapsed after theinitial charge of the secondary battery)̂B, and

the value calculated from a state of charge SOC of the secondary batteryis calculated using an expression including exp (C×SOC/T).

(8) A battery life estimation device including:

a storage section configured to store a plurality of types ofdegradation master data;

a condition setting section configured to set conditions related totemperature T provided for calculation and a battery state S providedfor the calculation; and

a controller configured to obtain a degradation estimation value,wherein

for a secondary battery having a degradation rate R when X days haveelapsed after initial charge of the secondary battery, the battery lifeestimation device is configured to calculate the degradation estimationvalue (X+Y) days after the initial charge from the degradation masterdata,

the controller is configured to select one of the plurality of types ofdegradation master data with use of the conditions set by the conditionsetting section, and

the controller is configured to derive number of elapsed days Xcorrgiving the degradation rate R based on the identified degradation masterdata, and to calculate the degradation estimation value (Xcorr+Y) daysafter the initial charge from the identified degradation master data.

(9) An electric vehicle including

a battery life estimation device including

a storage section configured to store a plurality of types ofdegradation master data,

a condition setting section configured to set conditions related totemperature T provided for calculation and a battery state S providedfor the calculation, and

a controller configured to obtain a degradation estimation value,wherein

for a secondary battery having a degradation rate R when X days haveelapsed after initial charge of the secondary battery, the battery lifeestimation device is configured to calculate the degradation estimationvalue (X+Y) days after the initial charge from the degradation masterdata, the secondary battery being configured to generate drive power ofthe vehicle,

the controller is configured to select one of the plurality of types ofdegradation master data with use of the conditions set by the conditionsetting section, and

the controller is configured to derive number of elapsed days Xcorrgiving the degradation rate R based on the identified degradation masterdata, and to calculate the degradation estimation value (Xcorr+Y) daysafter the initial charge from the identified degradation master data.

(10) An electric power supply apparatus including

a battery life estimation device including

a storage section configured to store a plurality of types ofdegradation master data,

a condition setting section configured to set conditions related totemperature T provided for calculation and a battery state S providedfor the calculation, and

a controller configured to obtain a degradation estimation value,wherein

for a secondary battery having a degradation rate R when X days haveelapsed after initial charge of the secondary battery, the battery lifeestimation device is configured to calculate the degradation estimationvalue (X+Y) days after the initial charge from the degradation masterdata, the secondary battery being configured to generate alternatingelectric power,

the controller is configured to select one of the plurality of types ofdegradation master data with use of the conditions set by the conditionsetting section, and

the controller is configured to derive number of elapsed days Xcorrgiving the degradation rate R based on the identified degradation masterdata, and to calculate the degradation estimation value (Xcorr+Y) daysafter the initial charge from the identified degradation master data.

[Modification]

Some embodiments of the present disclosure have been specificallydescribed above, which are not limitative. Various modifications basedon the technical idea of the present disclosure are possible. Forexample, the configurations, methods, processes, shapes, materials,numerical values, and the like described above in the embodiments aremere examples, and configurations, methods, processes, shapes,materials, numerical values, and the like different therefrom may beused as necessary.

Moreover, the configurations, methods, processes, shapes, materials,numerical values, and the like described above may be used incombination unless it is out of the gist of the present disclosure.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations, and alternations mayoccur depending on design requirements and other factors insofar as theyare within the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A method of estimating a battery life, the methodcomprising: for a secondary battery having a degradation rate R when Xdays have elapsed after initial charge of the secondary battery,calculating a degradation estimation value (X+Y) days after the initialcharge from degradation master data, the degradation master data beingidentified with use of conditions of temperature T provided for thecalculation and a battery state S provided for the calculation; andderiving number of elapsed days Xcorr giving the degradation rate Rbased on the identified degradation master data, and calculating thedegradation estimation value (Xcorr+Y) days after the initial chargefrom the identified degradation master data.
 2. The method according toclaim 1, wherein the secondary battery includes a cathode activematerial having an olivine structure.
 3. The method according to claim1, wherein the secondary battery is a lithium ion secondary batteryincluding LiFePO₄ as a cathode active material and including graphite asan anode active material.
 4. The method according to claim 2, whereinthe cathode active material having the olivine structure is one ofLiFePO₄ and LiMn_(x)Fe_(1-x)PO₄ where 0<x<1.
 5. The method according toclaim 1, wherein the conditions in estimation during the Y days areconfigured of n-number of conditions Z1, Z2, . . . , Zn where 1≦n, andtransition from first degradation master data to second degradationmaster data is performed to allow final degradation rate in the firstdegradation master data to be start degradation rate in the seconddegradation master data, the first degradation master data beingidentified by the condition Zn−1, and the second degradation data beingidentified by the condition Zn.
 6. The method according to claim 1,wherein, as the degradation master data, a value calculated based on aproduct of a value calculated from temperature of an outer wall of thesecondary battery, a value calculated from number of days that haveelapsed after the initial charge of the secondary battery, and a valuecalculated from a battery state of the secondary battery is used.
 7. Themethod according to claim 6, wherein the value calculated from thetemperature T of the outer wall of the secondary battery is calculatedusing an expression including exp (−A/T) where T is absolutetemperature, the value calculated from the number of days that haveelapsed after the initial charge of the secondary battery is calculatedusing an expression including (the number of days that have elapsedafter the initial charge of the secondary battery) ̂B, and the valuecalculated from a state of charge SOC of the secondary battery iscalculated using an expression including exp (C×SOC/T).
 8. A batterylife estimation device comprising: a storage section configured to storea plurality of types of degradation master data; a condition settingsection configured to set conditions related to temperature T providedfor calculation and a battery state S provided for the calculation; anda controller configured to obtain a degradation estimation value,wherein for a secondary battery having a degradation rate R when X dayshave elapsed after initial charge of the secondary battery, the batterylife estimation device is configured to calculate the degradationestimation value (X+Y) days after the initial charge from thedegradation master data, the controller is configured to select one ofthe plurality of types of degradation master data with use of theconditions set by the condition setting section, and the controller isconfigured to derive number of elapsed days Xcorr giving the degradationrate R based on the identified degradation master data, and to calculatethe degradation estimation value (Xcorr+Y) days after the initial chargefrom the identified degradation master data.
 9. An electric vehiclecomprising a battery life estimation device including a storage sectionconfigured to store a plurality of types of degradation master data, acondition setting section configured to set conditions related totemperature T provided for calculation and a battery state S providedfor the calculation, and a controller configured to obtain a degradationestimation value, wherein for a secondary battery having a degradationrate R when X days have elapsed after initial charge of the secondarybattery, the battery life estimation device is configured to calculatethe degradation estimation value (X+Y) days after the initial chargefrom the degradation master data, the secondary battery being configuredto generate drive power of the vehicle, the controller is configured toselect one of the plurality of types of degradation master data with useof the conditions set by the condition setting section, and thecontroller is configured to derive number of elapsed days Xcorr givingthe degradation rate R based on the identified degradation master data,and to calculate the degradation estimation value (Xcorr+Y) days afterthe initial charge from the identified degradation master data.
 10. Anelectric power supply apparatus comprising a battery life estimationdevice including a storage section configured to store a plurality oftypes of degradation master data, a condition setting section configuredto set conditions related to temperature T provided for calculation anda battery state S provided for the calculation, and a controllerconfigured to obtain a degradation estimation value, wherein for asecondary battery having a degradation rate R when X days have elapsedafter initial charge of the secondary battery, the battery lifeestimation device is configured to calculate the degradation estimationvalue (X+Y) days after the initial charge from the degradation masterdata, the secondary battery being configured to generate alternatingelectric power, the controller is configured to select one of theplurality of types of degradation master data with use of the conditionsset by the condition setting section, and the controller is configuredto derive number of elapsed days Xcorr giving the degradation rate Rbased on the identified degradation master data, and to calculate thedegradation estimation value (Xcorr+Y) days after the initial chargefrom the identified degradation master data.